Potassium chloride (“potash”) has many industrial uses, but is most commonly known as a component of agricultural fertilizers. Potash is typically extracted from underground sources either by conventional mining techniques or by solution mining. Once extracted, potassium chloride can be processed into a number of different finished forms or products suitable for specific industrial, chemical or agricultural applications as desired by individual customers.
Finished potassium chloride is typically sold in a granular form, and the purity and granule size may vary depending on the end use to which the product will be put. The grading of potash, and hence its market value are also dependent on both the purity and granule size of the product. Typically the potassium chloride is screened to the desired particle size for a particular need.
A typical potassium chloride feed stock, has a granule size that is comparable to table salt, which is less than the desired granule size. In order to obtain larger granules, this feedstock is first compacted using a simple roll compacter or the like to produce a sheet-like product. Subsequent processing typically involves controlled breakage of the potassium chloride sheet into granules, which are then sorted to a desired size range by screening or other methods known in the industry.
However, one of the limitations with compacted granular potassium chloride produced in this fashion has been that the product will physically break down when handled, stored or shipped. Given that granule size is an important feature in the finished product, breakage therefore diminishes the value of the finished product. These broken granules that arise from the handling of the finished product during processing are known as recycle or reclaim material. Such broken granules are collected or reclaimed from various areas during processing and can be mixed back into the feedstock and compacted again.
After the finished product leaves the plant, breakage diminishes the value of the product. Broken granules are smaller than the desired size and cause problems during the storage and handling of the finished product due to a tendency to generate dust and form clumps, a property known as “bridging.” Bridging impedes the flow of the product, and may result in significant storage problems. Excessive dust causes environmental concerns while uneven granule size can directly affect application rates.
Shipping of potash, typically by rail, is not a gentle process either in terms of the handling involved in the loading of rail cars or mechanical agitation during the extended movement of the rail cars themselves. Thus, storage, shipping and handling after the potash has left the mill can break up granules, with the result that over time undesirable characteristics occur in the product.
Therefore, it has been the desire of those in the field to find methods of producing an improved compacted granular potassium chloride product, with better shipping, handling and storage characteristics as compared to compacted potash products manufactured using prior art methods. Methods of production that improve the handling characteristics of compacted potash products and which result in a more durable finished product are of value as the result will be a more desirable and saleable commodity.